Positron Emission tomography (PET) imaging is an imaging technique that produces a three-dimensional image of body functioning. When a positron-emitting radioactive isotope (a tracer) is injected into the body on a biologically active molecule, a pair of gamma rays is indirectly emitted by the tracer. The pair of gamma rays is detected by the PET system and thusly provides an image of the body functioning.
A positron is a subatomic particle with the same mass as an electron and has an electronic charge of +1e, so the charge is numerically equal to an electron, but the positron has a positive charge. A positron is also called an anti-electron.
Positron emission is a type of radioactive decay. This occurs when a proton inside a radioactive isotope nucleus is converted to a neutron while releasing a positron and an electron neutrino. Gamma rays are also emitted during this decay. Gamma rays emit electromagnetic radiation at a high frequency.
Ammonia nitrogen 13 can be used for diagnostic purposes in positron emission tomography (PET) imaging. It is used in diagnosing cardiac disease and other cardiac-related problems in patients. In particular, ammonia nitrogen 13 is suitable for myocardial perfusion imaging by (PET).
When injected, ammonia nitrogen 13 is a positron emitting radiopharmaceutical. Nitrogen 13 decays by emitting a positron to Carbon 13. Nitrogen 13 is the longest-lived of the nitrogen radioisotopes, having a half-life of a bit less than ten minutes (9.965 minutes). While nitrogen 13 has the longest half-life of the nitrogen radioisotopes, the half-life of nitrogen 13 is rather short.
As a result of the very short half-life, the ammonia nitrogen 13 needs to be made as close to a PET suite as possible. Ammonia nitrogen 13 is produced in a cyclotron by bombarding water with protons producing a nuclear reaction. The result is ammonia nitrogen 13 and nitride and nitrite impurities.
Thus, if a PET suite uses ammonia nitrogen 13, then there needs to be a cyclotron within 15 minutes of the PET suite. Moreover, there needs to be system capable of purifying the ammonia nitrogen 13 before it is used in the PET application.
Overall, the process of producing ammonia nitrogen 13 for use in PET applications typically includes the use of a cyclotron to bombard oxygen 16 with hydrogen protons thereby producing nitrate and ammonia. Nitrogen 13 is a cyclotron produced radionuclide by a 16 O (p, α) 13 N irradiation reaction with protons. That is, when oxygen 16 is bombarded with protons, it causes the emission of α-particles and production of nitrogen 13. In PET applications nitrogen 13 is used as ammonia nitrogen 13. The reaction to produce nitrogen 13 is:16O+p=13N+α
Once the nitrogen 13 is produced, ammonia nitrogen 13 is produced by reduction of nitrogen 13 labeled nitrates and nitrites. Nitrogen 13 is converted to ammonia nitrogen 13 in aqueous medium, which is an exothermic reaction. In this reaction the major chemical species produced are nitrates, nitrites, ammonia and hydroxyl amine. Among them, the nitrates have the highest yield. The hydrogen evolved flushes out the ammonia nitrogen 13 and dissolves in saline solution. The mixture is passed through an anion-exchange resin to remove all anionic impurities, including nitrates and nitrites. The ammonia nitrogen 13 is filtered before use. Then, ammonia nitrogen 13 from the [13N] NH4+target appears in the desired chemical form. It needs to be trapped and filtered by passage through appropriate columns before being mixed with the correct substrate for dispensing NH3 in the form of NH4+ions.
More recently, the development of small cyclotrons has made it more desirable for hospitals or medical facilities to have on-site ammonia nitrogen 13 production for distribution to local PET suites. This has given rise to the need for the PET suite to have a suitable apparatus for purifying the ammonia nitrogen 13 and supplying it into a vial for use by the PET operator.
Previously, most such apparatuses were able to process only two vials of ammonia nitrogen 13 at a time. More recently, the apparatuses were able to process six vials of ammonia nitrogen 13 at a time.
That is, up to this point, most systems that are suited to delivering dosages of ammonia nitrogen 13 for purposes of PET imaging for cardiac patients are only capable of providing up to six dosages at a time. Moreover, these systems are not able to ensure minimal exposure to the radiation from ammonia nitrogen 13.
Thus, there is a need for a system that is capable of providing on demand ammonia nitrogen 13, while decreasing exposure to radiation.